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TitreBiotite chemistry as a monitor of magma fertility and mineralisation potential: results from the Devonian granitoids of New Brunswick
TéléchargerTéléchargement (publication entière)
AuteurAzadbakht, Z; Lentz, D R; McFarlane, C R M; Rogers, N
SourceTGI 4 - Intrusion Related Mineralisation Project: new vectors to buried porphyry-style mineralisation; par Rogers, N (éd.); Commission géologique du Canada, Dossier public 7843, 2015 p. 563-564, (Accès ouvert)
LiensCanadian Database of Geochemical Surveys, downloadable files
LiensBanque de données de levés géochimiques du Canada, fichiers téléchargeables
ÉditeurRessources naturelles Canada
Documentdossier public
Mediaen ligne; numérique
Référence reliéeCette publication est contenue dans Rogers, N; (2015). TGI 4 - Intrusion Related Mineralisation Project: new vectors to buried porphyry-style mineralisation, Commission géologique du Canada, Dossier public 7843
Référence reliéeCette publication est reliée les publications suivantes
SNRC21G; 21H; 21I; 21J; 21O; 21P
Lat/Long OENS -68.0000 -64.0000 48.0000 45.0000
Sujetsgisements porphyriques; cuivre porphyrique; prospection minière; minéralisation; biotite; tungstène; étain; molybdène; or; antimoine; roches magmatiques; roches intrusives; roches ignées; gisements filoniens; magmatisme; differentiation magmatique; gîtes magmatiques; géologie économique; pétrologie ignée et métamorphique; géochimie; Paléozoïque; Dévonien
Illustrationslocation maps; plots; photomicrographs
ProgrammeInitiative géoscientifique ciblée (IGC-4), Étude des gîtes porphyriques
Diffusé2015 06 11
Résumé(disponible en anglais seulement)
There are over 150 granitoid intrusions in the New Brunswick; however, all the mineralised intrusions formed in relation to Acadian and Neoacadian orogenic phases of Appalachian accretion. These granitoids range in age from 423 to 360 Ma, and include examples of pre-, syn-, late-, and post-tectonic emplacement with affinities ranging from primitive to highly evolved A-, S-, and I-types granitoids along with their hybrid varieties. Many of these are spatially and temporally related to specific styles of mineralization, producing deposits of Sn, Ta, Li, Sb, W, Mo, Cu, and Au, as well as other base-metals and U.
Igneous biotite crystallises over a wide range of conditions and reacts very sensitively to physio-chemical conditions like halogen and oxygen fugacities, pressure, temperature and chemical composition of the magmas. This sensitivity makes biotite a suitable mineral for identifying the petrogenetic processes, mineralization and alteration of the host granitic rocks. The following features make biotite a valuable probe of magma composition: i) It is the most important reservoir of any excess aluminium in granites that do not contain modal garnet, cordierite, or the Al2SiO5 polymorphs; therefore, it directly reflects the peraluminosity of the host magma in such rocks; ii) it is the most readily available indicator of oxidation state; and iii) it can provide information about the F and Cl composition of the magma.
Previous studies have shown that biotite, and to lesser extent hornblende and magnetite, continuously equilibrates with host liquids. Consequently, a core-to-rim study of these minerals and their compositional zoning can provide a record of magma evolution so that the origin and evolution of granitoids can be documented. The aim of this study is to calculate fluoride and chloride activity of aqueous fluids based on measuring F and Cl contents in the minerals containing hydroxyl and halogens, using a combination of electron microprobe and Laser Ablation ICP-MS. These data will be combined and compared with whole-rock trace element geochemistry. The results are expected to help constrain crystallisation conditions, volatile exsolution, and fluorine-chlorine activity of fluids associated with these intrusions, and also to examine the degree of subsolidus re-equilibration using various geothermobarometry techniques. By linking these results to the various styles/types of granitoids and their associated mineralisation it is hoped to establish biotite composition as a robust indicator of an intrusions ore potential.